Process of producing alpha



United States Patent D PROCESS OF PRODUCING ALPHA, ALPHA-DI- CHLORO-EPSILON-CAPROLACTAM Thomas R. Hopkins, .lophn, Mo., William C. Francis, Pittsburg, Kans., and James C. Werner, Joplin, Mo., assignors to Spencer Chemical Company, a corporation of Missouri No Drawing. Application March 30, 1956 Serial No. 574,968

8 Claims. (Cl. 260-2393) This invention relates to processes of producing chemical compounds. More particularly, this invention is concerned with a process of producing alpha, alpha-dichloroepsilon-caprolactam of the formula has the advantages of especially high yields of alpha,

alpha-dichloro-epsilon-caprolactam, as contrasted with the prior art, and facilitates the isolation and recovery of the product.

This process may be represented as follows:

\ 1. Chlorination on, 31 01, (or 3P on 3012 i P001, NH-C a I 30in P C13 Reaction product 2P Cl; P C1; 3H0] ii 2. Hydrolysis As shown, the chlorination of epsilon-caprolactam with PCl results in the attendant production of P01 and POCl as by-products. Part or all of the POC1 formed as a by-product may be used as additional reaction medium while the PCI;, may be treated with chlorine to convert it to PCl for use in chlorinating additional epsiloncaprolactam.

The chlorination of epsilon-caprolactam with PCl in POC1 may be effected at a reaction temperature above 50 C. and preferably at 80-85 C. The rate of reaction will vary with the temperature although 1 to 5 hours usually is sufficient for substantial completion of the reaction. Stoichiometric amounts of reactants are generally used, i. e., one mole of epsilon-caprolactam and three moles of PCl although an excess of the latter may be used.

To suppress or prevent side reactions, it has been found advantageous to first mix epsilon-caprolactam and the PCl and preferably these two reactants together with P001 at a temperature maintained below 35 C. and

above the freezing point of the mixture, and to then effect chlorination at above 50 C. The combined reactants need not be maintained below 35 C. any longer than it takes' to mix the quantities together.

After the chlorination step has been terminated, the reaction mixture is distilled, preferably under reduced pressure, until all volatile products including POCl PCl and HCl are removed. The residue is then hydrolyzed over ice or in a dilute aqueous alkali, such as sodium carbonate. Alpha, alpha dichloro epsilon caprolactam precipitates from the aqueous mixture and may be conveniently recovered by filtration. It may be purified as by recrystallization from ligroin.

The PCl and P001 by-products of the chlorination step may be distilled and recovered as a mixture. This mixture may then be treated with chlorine gas to convert PCl to PO1 The resulting mixture of PCl and POCl may be recycled for chlorinating additional epsiloncaprolactam, but preferably these two components are first separated by conventional methods and each material recycled in an amount desired. In this way an otherwise undesirable excess of POCl in the reactor is prevented.

It should be noted that the two moles of P01 which form in the chlorination step give two moles of PCl when treated with chlorine so that of the three moles of PCl used originally, two moles of P01 are regenerated and charged to the process.

The excess POCl which may accumulate and not find use in the process may be readily converted to ammonium phosphate, which product is of value as a fertilizer and basic chemical of commerce.

Alpha, alpha-dichloro-epsilon-caprolactam is converted to alpha-chloro-epsilon-caprolactam by the use of hydrogen with a catalyst such as palladium on charcoal and pressures of about five atmospheres at room temperature. The resulting alpha-chloro-epsilon-caprolactam may then be converted to lysine as shown in Serial No. 574,967, filed March 30, 1956.

The following examples are intended for purposes of illustration and are not to limit the scope of this invention as modifications will be obvious to those skilled in the art.

Example 1 17 gms. (0.15 mole) of epsilon-caprolactam dissolved in 50 mls. of P001 was added dropwise, and at such a rate as to maintain a reaction temperature of 78-82 C., to a stirred solution of 94 gms. (0.45 mole) of PCl in mls. of POC1 When addition was complete, the stirred mixture was heated to reflux (104 C.) for a period of 15 minutes. The solvent and volatile by-products were removed by vacuum distillation and the liquid residue added portionwise to cracked ice. On allowing the solution to warm to room temperature there was obtained by filtration 18.3 gms. (67% yield) of alpha, alphadichloro-epsilon-caprolactam, M. P. 123-126 C.

Example 2 To 94 gms. (0.45 mole) of P01 there was slowly added 17 gms. (0.15 mole) of epsilon-caprolactam in such a manner as to maintain the temperature of the mixture at 27-32 C. There Was then added 60 mls. of POC1 and the temperature adjusted to 70 C. for a period of 1 hour. The reaction mixture was cooled and concentrated by vacuum distillation. The residue was hydrolyzed with cracked ice and the crystalline product removed by filtration followed by water washing and drying to yield 24 gms. (87.9% yield) of alpha, alpha-dichloro-epsiloncaprolactam, M. P. 123-125 C.

Example 3 A run similar to Example 1 was conducted with 188 gms. (0.91 mole) of PC1 and 34 gms. (0.30 mole) of Patented Apr. 29, 1958 3 epsilon-caprolactam whereinthetemperature of the PC1 lactam mixture was maintained at l5 C. during their introduction. 50 mls. of POCl was added at -70 C. and the reaction temperature then held at 70 C. for 2 hours to produce 49.7 gms. (91.1% yield) of alpha, alpha-dichloroepsilomcaprolactam, M. P. 121-l23 '6.

Example 4 The distillate obtained from Example 1, comprising a mixture of PCl and POCl was treated with an equiva lent amount of chlorine gas to convert the PCl to l 'CA An amount of epsilon caprolactam in the ratio of 1:3 moles of lactam:PCl was introduced and the mixture refluxed for approximately 15 minutes. This reaction product was'then concentrated under reduced pressure,

and the oily residue hydrolyzed in ice water-followed neutralization with sodium carbonate to give a 67% yield of crude alpha, alpha-dichloro-epsilon-caprolactam, M. l19-l22 C.

Various changes and modifications of the invention can be made and, to the extent that such variations incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.

What is claimed is:

l. The process which comprises chlorinating epsiloncaprolactam with PCl in the presence of added POCl and hydrolyzing the reaction product to form alpha, alphadichloro-epsilon-caprolactam.

2. The process of claim 1 in which the chlorination is eifected above 50 C.

3. The process of claim 1 in which the chlorination is efiected .at 80-85 C.

4. The process which comprises mixing epsilon-caprolactam with PCI:, while maintaining the temperature of the mixture below C., reacting said substances in the presence of added POC1 at a temperature above C., and hydrolyzing the reaction product to form alpha, alpha-dichloro-epsilon-caprolactam.

5. The process which comprises mixing epsilon-capro lactam, PCl and POCl while maintaining the temperature of the mixture at about 5 C. to 35 C., effecting the chlorination at a temperature above 50 C., distilling off the solvent and volatile by-products, and hydrolyzing the residue to form alpha, alpha-dichloro-epsilon-caprolactam.

6. The process which comprises reacting epsilon-caprolactam with PC1 in the presence of added POCl distilling off the volatiles including the by-products PCl and POCig hydrolyzing the residue to form alpha, alphadichloro-epsilon-caprolactam, treating the PCl with chlorine to form PCI recycling the PCl so formed and reacting it with additional epsilon-caprolactam in the presence of POCI 7. The process which comprises reacting epsilon-captolactam with PCl in the presence of added P0Cl above 50 C., distilling off the volatiles including the by-products PCl and POCl hydrolyzing the residue to form alpha, alpha-dichloro-epsilon-caprolactam, treating the PCl with chlorine to form PCI recycling the PCI,; so formed and part of the POCl and mixing the PO1 and P0Cl with additional epsilon-caprolactam.

8. The process which comprises mixing epsilon-captolactam with PCl in the presence of added POCl while maintaining the temperature of the mixture at about 5 C. to 35 C., eifecting the chlorination at a temperature above 50 C., distilling oil the volatiles including the by-products PCl and POCl hydrolyzing the residue to form alpha, alpha-dichloro-epsilon-caprolactam, treating the PC13 with chlorine to form PO1 recycling the PC1 so formed and part of the POCl and mixing the PCl and P001 with additional epsilon-caprolactam.

References Cited in the file of this patent Von Braun: Ber., vol. 63, pp. 502-057 (1930).

UNHED STATES PATENT @FFICE @ERTEFICATE or CORREQTION Patent No, 2,832,769 April 29, 1958 Thomas Ro Hopkins et al0 It is hereby certified that error appears in the printed specification of the above numbered patent requiring co Patent should read as corrected below,

Golunm 4, line 36,. list of references cited, for "pp, 502*05'7" read ppo 502 50? Signed and sealed this 15th day of July 19580 (SEAL) Attest:

KARL AXLINE ROBERT C. WATSON Attesting ()fiicer Commissioner of Patents rrection and that the said Letters 

1. THE PROCESS WHICH COMPRISES CHLORINATING EPSILONCAPROLACTAM WITH PCL5 IN THE PRESENCE OF ADDED POCL3 AND HYDROLYZING THE REACTION PRODUCT TO FORM ALPHA, ALPHADICHLORO-EPSILON-CAPROLACTAM. 